(1) Field of the Invention
The invention relates generally to electronic circuits within optical read-out systems and in particular to interfaces for operating light emitting diodes (LED) in conjunction with photo diodes realized with integrated-circuit technologies.
(2) Description of the Prior Art
Special interface and driver circuits in electronic applications are required, when it comes to operating LEDs and photo diodes within control systems, where a photo sensor measures the emitted radiation from a photon source and the result of this operation is further processed in subsequent control circuits. This is a noted and quite common application of such electronic components very frequently employed in many industrial systems; for example for monitoring and surveillance purposes with light barriers within a process control of plants, for distance/thickness measuring, for touch or biometric sensor systems, for position detection systems, or for remote control systems, wireless data transmission systems and so on. Therefore the reliable and cost-effective manufacturing of such circuits, at its best containing all the necessary components within one single integrated circuit is a desirable demand.
Realizations of the prior art for such systems are often implemented as specifically assembled semiconductor circuit systems, consisting of integrated control circuits combined with separate, externally adapted photo devices considering the specific operational requirements. Therefore, when photo diodes as sensor devices are used, the configuration shown in FIG. 1A prior art is commonly used. As photo sensor a discrete photo diode component, connected to its supply voltage VD (Photo diode) is used, further connected via a pad/pin to the evaluation electronics circuit (IC), containing the operational amplifier for the photo currents with its necessary stabilizing feedback resistor, eventually ameliorating its dynamic behavior with a capacitor (Amplifier), also containing the signal processing part for the particular control functions (Control) supplying the output signal of the circuit (Output). This configuration is realizing only the photo sensor input part of the abovementioned, widely used prior art control systems. As can be seen from this example, beneath specialized integrated circuits usually incorporating CMOS (Complementary MOS) devices always some additional external and discrete components are employed, which are normally realized with other semiconductor technologies. In some cases there is additional on chip AC coupling employed, using an extra band pass filter. All this leads to more complex and thus expensive solutions. It is therefore a challenge for the designer of such circuits to achieve a high quality, but lower-cost solution.
There are several efforts and labors with various patents referring to such approaches.
U.S. Pat. No. 5,822,099 (to Takamatsu) describes a light communication system employing light, such as infrared rays, in which power consumption required for light communication is diminished for prolonging the service life of portable equipments and for reducing interference or obstruction affecting other spatial light communication operations. A light emitting element in a transmission portion of a first transmission/reception device is controlled in light emission by a light emission driving control circuit and has its light emission intensity adjusted by a light emission intensity adjustment circuit in a light emission drive control circuit. The light reception intensity in a light receiving element of a receiving portion of a second transmission/reception device is detected by a reception light intensity detection circuit in a light signal reception processing circuit and sent via a transmission driving control circuit and a transmitting portion so as to be received by a reception portion of the first transmission/reception device. The reception light intensity information is taken out by a reception processing circuit and supplied to the light emission intensity adjustment circuit. The light emission intensity adjustment circuit is responsive to the reception light intensity information to adjust the light-emitting element to a light emission intensity that is of a necessary minimum value to permit stable light communication.
U.S. Pat. No. 6,236,037 (to Asada, et al.) shows finger touch sensors and virtual switch panels for detecting contact pressure applied to a finger, the finger having a fingernail illuminated by light, comprises at least one photo detector for measuring a change in light reflected by an area of the finger beneath the fingernail in response to the contact pressure applied to the finger. The photo detector provides a signal corresponding to the change in light reflected. The device also includes a processor for receiving the signal and determining whether the change corresponds to a specified condition. The photo detector may be enclosed in a housing and coupled to the fingernail.
U.S. Pat. No. 6,337,678 (to Fish) explains a force feedback computer input and output device with coordinated haptic elements, where a set of haptic elements (haptels) are arranged in a grid. Each haptel is a haptic feedback device with linear motion and a touchable surface substantially perpendicular to the direction of motion. In a preferred embodiment, each haptel has a position sensor, which measures the vertical position of the surface within its range of travel, a linear actuator that provides a controllable vertical bi-directional feedback force, and a touch location sensor on the touchable surface. All haptels have their sensors and effectors interfaced to a control processor. The touch location sensor readings are processed and sent to a computer, which returns the type of haptic response to use for each touch in progress. The control processor reads the position sensors, derives velocity, acceleration, net force and applied force measurements, and computes the desired force response for each haptel. The haptels are coordinated such that force feedback for a single touch is distributed across all haptels involved. This enables the feel of the haptic response to be independent of where touch is located and how many haptels are involved in the touch. As a touch moves across the device, haptels are added and removed from the coordination set such that the user experiences an uninterrupted haptic effect. Because the touch surface is comprised of a multiple haptels, the device can provide multiple simultaneous interactions, limited only by the size of the surface and the number of haptels. The size of the haptels determines the minimum distance between independent touches on the surface, but otherwise does not affect the properties of the device. Thus, the device is a pointing device for graphical user interfaces, which provides dynamic haptic feedback under application control for multiple simultaneous interactions.
U.S. Pat. No. 6,492,650 (to Imai, et al.) discloses a sensor unit for use in a multiple sensor unit array, which comprises a housing which is adapted to be mounted on a DIN rail closely one next to another as a sensor unit array, and to be connected to a sensor head via a cable. The housing accommodates a sensing circuit system for achieving a desired sensing function in cooperation with the sensor head, a first optical communication circuit system including a light emitting device and a light receiving device for conducting an optical bi-directional communication with one of the adjacent sensor units in the multiple sensor unit array, and a second optical communication circuit system including a light emitting device and a light receiving device for conducting an optical bi-directional communication with the other of the adjacent sensor units, whereby the sensor unit is enabled to conduct an optical bi-directional communication with each of the adjacent sensor units in the multiple sensor unit array.